1. Field of the Invention
The invention relates generally to a control device and control method for a vehicle. More specifically, the invention relates to a technology that sets a cancellation condition for canceling a fuel supply cut-off to an engine.
2. Description of the Related Art
Typically, in order to enhance fuel efficiency, a “fuel supply cut-off” control that cuts off a fuel supply (injection) to an engine is executed when a vehicle is decelerating. When the running condition of the vehicle satisfies a cancellation condition for canceling the fuel supply cut-off mode, the fuel supply to the engine is restarted. Namely, the fuel supply cut-off mode is cancelled. Thus, the power transfer state is switched from an “engine driven state” in which the engine is driven by the power transferred from a transmission to an “engine drive state” in which the transmission is driven by the power from the engine. Accordingly, when the fuel supply cut-off mode is cancelled, shock may be caused. Especially, because a load due to an auxiliary mechanism driven by the power from the engine is great, the target idle speed is set to a high value. Therefore, when the engine speed is increased up to the target idle speed by canceling the fuel supply cut-off mode, the power transfer state is switched from the “engine driven state” to the “engine drive state” and shock may be caused. In order to minimize such shock, a technology for reducing the output of the engine has been proposed when the fuel supply cut-off mode is cancelled.
Japanese Patent Application Publication No. 2004-197595 (hereinafter, referred to as “JP-A-2004-197595”) describes a shift control apparatus for a vehicle automatic transmission that includes an automatic transmission and a fuel supply cut-off device that cuts off a fuel supply to an engine if the engine speed exceeds a threshold value when the vehicle is decelerating. The shift control apparatus described in JP-A-2004-197595 further includes a fuel supply cut-off mode cancellation determination unit that determines whether the fuel supply cut-off performed by the fuel supply cut-off device has been cancelled and the fuel supply to the engine has been restarted; an engine drive state predicting unit that predicts whether the automatic transmission will be brought into the “engine drive state” if the fuel supply cut-off mode cancellation determination unit determines that the fuel supply to the engine has been restarted; and an engine output reduction unit that reduces the output of the engine if the engine drive state predicting unit predicts that the automatic transmission will be brought into the “engine drive state”.
With the shift control apparatus described in JP-A-2004-197595, if the engine drive state predicting unit predicts that the automatic transmission will be brought into the “engine drive state” when the fuel supply cut-off mode cancellation determination unit determines that the fuel supply to the engine has been restarted, the engine output reduction unit reduces the output of the engine. It is therefore possible to appropriately suppress shock and noise that are caused even if the fuel supply to the engine is restarted.
However, in the shift control apparatus described in JP-A-2004-197595, an extra control for reducing the output of the engine needs to be executed. In addition, constants used in the control based on the output of the engine, the control for reducing the output of the engine, etc. need to be accurately set by repeating experiments and simulations. This causes the inconvenience, that is, setting the constants used in these controls takes a lot of time.